title: Relation between lower extremity alignment and proximal femur anatomy. Parameters during total hip arthroplasty.
abstract: BACKGROUND
  Lower extremity alignment correlates with native femoral offset. Eventual impact of the change in femoral offset induced by total hip arthroplasty (THA) on lower extremity alignment has not been documented.
  
  
  OBJECTIVE
  THA significantly changes lower extremity alignment, and the change correlates with the change in femoral offset.
  
  
  METHODS
  We conducted a prospective study of 200 patients with primary hip osteoarthritis or avascular femoral head necrosis who underwent cementless THA. Pre-operative computed-tomography templating was performed and the femoral component was then custom-manufactured to replicate the native femoral anatomy. Mean age was 58 years (range, 28-83 years). Before and at least two years after THA, two observers who were not involved in the surgical procedures used standing antero-posterior long-leg radiographs to determine the mechanical axis of the lower-limb (hip-knee-ankle [HKA] angle), femoral offset, neck-shaft angle (NSA), and lower-limb length discrepancy (LLLD).
  
  
  RESULTS
  Mean values pre-operatively and at last follow-up were as follows: HKA angle, 179.2° ± 3.9° (range, 170.5° to 190.5°) and 177.7° ± 3.5°(range, 173° to 187°); LLLD, -0.7 mm (range, -30 mm to +25 mm) and +5.1 mm (range, -7 mm to +21 mm); NSA, 134° ± 7.5° (range, 100° to 124°) and 135° ± 4.2° (range, 124° to 146°); and femoral offset, 42 ± 7.8 mm (range, 24 mm to 68 mm) and 49 ± 7.5 mm (range, 33 mm to 70 mm). Although THA significantly altered lower-limb alignment, univariate and multivariate analyses showed no significant association between the change in HKA angle and the change in femoral offset.
  
  
  CONCLUSIONS
  Lower-limb alignment was significantly affected by THA, although the HKA angle changes were small. The small impact of THA on HKA angle values may be ascribable to efforts aimed at replicating the native femoral offset during arthroplasty, as well as to the limited sample size and to potential measurement errors related to the small size of the changes. Our results suggest that, provided careful attention is directed to replicating the native femoral offset, THA in patients with limited pre-operative anatomical abnormalities may have no major impact on the biomechanical parameters of the ipsilateral knee.
  
  
  METHODS
  Level III, prospective diagnostic study.
authors.affiliation: Motion research and musculo-skeletal institute, Southern Teaching Hospital Center, Sainte-Marguerite Hospital, 270, boulevard Sainte-Marguerite, 13009 Marseille, France.
authors.forename: M
authors.initials: M
authors.lastname: Ollivier
authors.forename: S
authors.initials: S
authors.lastname: Parratte
authors.forename: L
authors.initials: L
authors.lastname: Lecoz
authors.forename: X
authors.initials: X
authors.lastname: Flecher
authors.forename: J-N
authors.initials: JN
authors.lastname: Argenson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000843:Ankle Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D001843:Bone Cements; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000517:prevention & control*; D015331:Cohort Studies; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000601:surgery*; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D007870:Leg Length Inequality / Q000000981:diagnostic imaging / Q000517:prevention & control; D035002:Lower Extremity / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015588:Observer Variation; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000601:surgery*; D011182:Postoperative Care; D011300:Preoperative Care; D011446:Prospective Studies; D015203:Reproducibility of Results; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
chemical_list: D001843:Bone Cements
keywords: Adult; Biomechanics; Femoral offset; Lower extremit alignment; Total hip arthroplasty